Sanitary napkins are made of three separate components. An absorbent component is generally covered by a fluid permeable nonwoven cover material which is designed to abut the body of the wearer. A fluid impermeable baffle is provided to prevent leakage from the absorbent portion of the napkin into the garment of the wearer.
These baffles may be positioned directly against the absorbent with the cover in the form of a wrap which extends over and surrounds the baffle, or the baffle may be external to the wrap thereby providing an outer bottom-most surface for the sanitary napkin. Over the past decade, sanitary napkins having these external baffles have become more prevalent. One of the reasons for this is the increasing popularity of napkins of reduced bulk. These napkins which are of the panty liner or the maxi thin type do not require the cover to function as a complete pad wrap for purposes of stability. Also, ease of manufacture of these napkins dictates that the baffle be placed externally to the other components on the bottom of the napkin. Baffles have traditionally been made of a thermoplastic film which, while thin and inexpensive, tend to make noise when the wearer walks and also chafe the wearer's skin. In addition, while these baffles are fluid impermeable, they are also vapor impermeable. This means that perspiration resulting from wear is not easily removable from the napkin and vaporized moisture from napkin discharge remains within the napkin confines. Of course, this gas impermeable baffle prevents circulation of air which intensifies the odors associated with menstruation.
In addition, baffles which are external to the other napkin components, must have sufficient strength and integrity to receive garment attachment adhesive and resist tearing after the garment attachment adhesive is removed from the undergarment of the wearer when the napkin is changed.
Several attempts have been made in the past to design an acceptable fluid impermeable moisture permeable baffle. Representative prior art is U.S. Pat. No. 3,595,235 which discloses such a baffle without a description of how it is to be provided. U.S. Pat. No. 3,989,867 which discloses a baffle made of tapered hollow bosses in a polyethylene film which is allegedly impervious to fluids while pervious to gases. British Patent Application No. 2,035,092 discloses a backing for an absorbent article formed of a polyester-rayon nonwoven with coating of a liquid repellent breathable adhesive. U.S. Pat. No. 4,338,371 discloses a liquid impermeable gas permeable backing of spandex polyolefin fibers. U.S. Pat. No. 4,240,416 discloses a nonwoven cover of binder free synthetic fibers i.e., a spunbonded nonwoven web which has a wetting agent coated only on the body contact side. The patent discloses that the untreated back of this web is air permeable and fluid penetration resistant. U.S. Pat. No. 4,059,114 discloses a panty liner product with a meltblown baffle which is supposedly fluid impermeable and gas permeable made from a meltblown web of polypropylene fibers. There are several other patents, in addition, which treat coating of cellulosic material to withstand fluid penetration and depending on the nature of the treatment, these baffle layers may also be gas permeable.
Each of these patents provides baffles which are defective either from the standpoint of effective fluid blocking, strength which will resist tearing while providing a suitable adhesive anchor for garment attachment adhesive, or softness and quietness.